1. Field of the Invention
The present invention relates to a switch unit and an electronic device including the switch unit.
2. Description of the Related Art
A sheet switch in which a metal dome is arranged on a printed wiring board and a sheet is attached thereto is known as discussed in Japanese Patent Application Laid-Open No. 2010-192199. A contact pattern formed on the printed wiring board is surface-treated with electrolytic gold plating to secure stable contact reliability with the metal dome. In this case, the printed wiring board needs a pattern called a plating bar connected up to an outline end of the board to surface-treat the contact pattern with electrolytic gold plating at the time of manufacture as discussed in Japanese Patent Application Laid-Open No. 2003-347699.
However, in some cases, it is difficult to pull out the pattern to be plated up to the outline end. In such a case, other patterns whose plating bar is pulled out to the outline end and the pattern whose plating bar cannot be pulled out to the outline end are connected inside the board and after plating is performed, the connection portion of mutual patterns are drilled to disconnect the mutual patterns.
If the plating bar disconnection hole is present in an attachment portion of the sheet switch, the plating bar exposed to an end face of the plating bar disconnection hole and an adhesive of the sheet switch may come into contact.
If an electronic device is used in a very humid environment, patterns disconnected by the plating bar disconnection hole may be allowed to be conductive due to moisture absorption of the adhesive, leading to a malfunction of the device. To avoid such a malfunction, forming an opening in the sheet switch so as not to cover the plating bar disconnection hole can be considered. In this case, however, patterns are exposed from the end face of the plating bar disconnection hole. Thus, if static electricity passes through a gap between an exterior cover of the electronic device and the key top of the switch, the static electricity that has passed flows from the end face to the exposed pattern, causing an issue of a malfunction of the electronic device.
In consideration of the above point, it is necessary to position the plating bar disconnection hole sufficiently remotely from the gap between the exterior cover and the key top, but sufficient measures may not be executable due to miniaturization of an electronic device or for the convenience of wiring of a printed wiring board.